An OLED (Organic Light-Emitting Diode) display apparatus comprises a substrate, an OLED, a packaging layer and a packaging coverplate, and the OLED comprises an anode, an organic layer (including a hole transport layer and an electron transport layer, and an organic light-emitting layer located between the hole transport layer and the electron transport layer) and a cathode. As compared with the LCD display apparatus, the OLED display apparatus has the following advantages: thin display panel, light weight, wide viewing angle, active light emission, continuous and adjustable color of emitted light, low cost, fast response, low energy consumption, low driving voltage, a wide range of operating temperatures, simple production process, high light-emitting efficiency, and ability to realize flexible display. The OLED attracts much attention from industrial and scientific fields due to its advantages that other displays could not match and good application prospect.
Studies have shown that water vapor, oxygen and the like in the air have great impact on the service life of the OLED for the following main reasons: (1) when the OLED works, electrons are to be injected into the cathode, which requires the work function of the cathode to be lower, but metallic materials, such as aluminum, magnesium, calcium, etc, which are common materials of the cathode, are usually active and apt to react with water vapor permeating into the OLED; (2) the water vapor will also react with the hole transport layer and the electron transport layer, which will cause failure of the OLED. Therefore, it is necessary to effectively package the OLED to isolate functional layers of the device from the water vapor, oxygen and the like in the air, whereby the service life of the device can be prolonged.
At present, a relatively effective method of packaging the OLED is to manufacture a single thin film or multiple thin films on the substrate and the functional layers so as to prevent the permeation of water, oxygen and other ingredients. A traditional water vapor barrier layer is a packaging layer formed by the combination of an inorganic layer and an organic layer. The inorganic layer could better prevent the permeation of water and oxygen, but there are some shortcomings in its manufacturing process, it has low elasticity and relatively large internal stress and is easy to peel off from the OLED. Therefore, it is required to combine the inorganic layer and the organic layer for packaging. Although the organic layer does not do well in isolating water and oxygen, the organic material itself exhibits certain water absorbency as well as relatively good bonding effect, and thus can ensure that the OLED and the inorganic layer are well bonded. However, since such multilayer structure comprises multiple layers having different refractive indexes, when light passes through the layers directly, total internal reflection will occur at interfaces between the layers, which will reduce the output of light. Furthermore, this part of light will be converted into heat to damage the OLED.